Merged magnetic head with a first pole piece notching layer

ABSTRACT

A single-sided, notched write head is provided for writing narrow erase band servo tracks as well as a double-notched write head, and for writing data tracks better than a double-notched write head. The single-sided, notched write head writes a narrow erase band on the notched side and a wide erase band on the unnotched side. In one embodiment, only one side of the first pole piece layer is notched, and in another embodiment a first side of the first pole piece layer is notched more than a second side. By writing servo tracks only a fraction of the track width of the write head, a wide erase band region is overwritten so that a narrow erase band is on each side of the servo track. Data tracks are written with a narrow erase band on one side and a wide erase band on the other side. The wide erase band on one side of the data track allows more flexibility in spacing the read head from adjacent tracks. The single-sided, notched write head can be manufactured with methods that require less processing time than a double-notched write head. In one method, a notching layer is employed where removal of a small corner of the notching layer provides the first pole piece with a notch. Other methods employ photoresist to protect the side of the first pole piece that is not to be notched, and/or oscillating the workpiece less than 360° so that milling is more concentrated at the notch site.

CROSS REFERENCE TO RELATED PATENTS

Cross reference is made to commonly assigned U.S. Pat. No. 5,438,747 andcommonly assigned U.S. Pat. No. 5,452,164 which are incorporated byreference herein.

REFERENCE TO RELATED APPLICATION

This is a continuation application of application Ser. No. 08/876,451filed Jun. 16, 1997, now U.S. Pat. No. 6,201,670 B1.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a merged MR head made by notching thefirst pole piece of the head's write element with a notching layer, andalso to forming a notched first pole piece with a first pole piece layerand the notching layer, and then milling a second pole piece layer, agap layer and the notching layer until side walls of the second polepiece layer, gap layer and notching layer are contiguous.

2. Description of the Related Art

A write head is typically combined with a magnetoresistive (MR) readhead to form a merged MR head, certain elements of which are exposed atan air bearing surface (ABS). The write head comprises first and secondpole pieces connected at a back gap that is recessed from the ABS. Thefirst and second pole pieces have first and second pole tips,respectively, which terminate at the ABS. An insulation stack, whichcomprises a plurality of insulation layers, is sandwiched between thefirst and second pole pieces, and a coil layer is embedded in theinsulation stack. A processing circuit is connected to the coil layerfor conducting write current through the coil layer which, in turn,induces write fields in the first and second pole pieces. A non-magneticgap layer is sandwiched between the first and second pole tips. Writefields of the first and second pole tips at the ABS fringe across thegap layer. In a magnetic disk drive, a magnetic disk is rotated adjacentto, and a short distance (fly height) from, the ABS so that the writefields magnetize the disk along circular tracks. The written circulartracks then contain information in the form of magnetized segments withfields detectable by the MR read head.

The MR read head includes an MR sensor sandwiched between first andsecond non-magnetic gap layers, and located at the ABS. The first andsecond gap layers and the MR sensor are sandwiched between first andsecond shield layers. In a merged MR head, the second shield layer andthe first pole piece are a common layer. The MR sensor detects magneticfields from the rotating disk by a change in resistance that correspondsto the strength of the fields. A sense current is conducted through theMR sensor, where changed in resistance cause voltage changes that arereceived by the processing circuitry as readback signals. One or moremerged MR heads may be employed in a magnetic disk drive for reading andwriting information on circular tracks of a rotating disk.

Good design dictates that the write head writes with a wide trackprofile, while the read head reads a more narrow track profile in orderthat the read head not pick up signals from adjacent tracks in thepresence of track misregistration. Signals picked up from adjacenttracks result in poor readback performance. The write head is alsoemployed to write servo signals on the magnetic disk, in spaced apartsectors dedicated for servo signals. The disk typically has allocatedregions dedicated for the imbedded servo information. The servo signalsare read by the read head and employed by servo processing circuitry tomaintain the write head on track.

In the prior art, the first pole piece layer of the write head has beennotched to improve its servo writing performance. The notching forms aportion of the first pole piece into a pedestal with first and secondside walls that align with first and second side walls of the secondpole tip. With notching, the fringe field at the gap between the secondpole tip and the first pole piece is limited to the width of the secondpole tip, which defines the width of tracks written on a disk. This isbecause the field is captured by the pedestal instead of spreading outlaterally to the flat portion of the first pole piece on each side ofthe second pole tip. Accordingly, tracks on the magnetic disk havenarrow erase bands. From a servo perspective, narrow erase bands improvethe quality of the servo pattern which consists of phase alignedtransitions. However, data tracks favor wider erase bands whichdiminishes interference from adjacent tracks in the presence of trackmisregistration. Since servoing cannot be sacrificed, there is a strongfelt need for a write head that writes good servo tracks, but is betterthan the prior art at writing data tracks.

Typically, a second pole piece, along with its second pole tip, isconstructed by frame-plating it on top of the gap layer. Afterdepositing a seed layer on the gap layer, a photoresist layer is spun onthe seed layer, imaged with light, and developed to provide an openingsurrounded by a resist wall for plating the second pole piece with itssecond pole tip. To produce a second pole tip with a narrow track width,the photo-resist layer has to be relatively thin. This relationship,referred to as the “aspect ratio”, is the ratio of the thickness of thephotoresist layer in the pole tip region to the track width of thesecond pole tip. Preferably, the aspect ratio should be on the order ofthree. In other words, for a track width of 1 μm, the thickness of thephotoresist in the pole tip region should be about 3 μm. If thephotoresist is thicker than this, the side walls of the second pole tip,especially at the base, will not be well formed due to scattering oflight as it penetrates the photoresist layer during the imaging step.

A prior art process for notching the first pole piece entails ion beammilling the gap layer and the first pole piece, employing the secondpole tip as a mask. According to this prior art process (typified inU.S. Pat. No. 5,452,164 and U.S. Pat. No. 5,438,747), a full film gaplayer is formed on a first pole piece layer, followed by frame plating asecond pole piece layer and pole tip on the gap layer. The second poletip layer is employed as a mask during milling of notches in the secondpole tip layer. The direction of milling beam forms an angle to avertical axis while the workpiece is rotated. The procedure first millsthrough the gap layer, and next mills the first pole piece layer to formthe notches. Since each notch site is directly below a respective sidewall of the second pole tip, each notch site is milled for about 180° ofthe rotation, and then is shadowed by the second pole tip, preventingmilling for the next 180° of rotation.

In order to account for windage (material consumed by processing), thesecond pole tip is frame plated, wider than a desired target trackwidth, and thicker than a desired height. During milling of the gaplayer to form the write gap, the top and first and second side walls ofthe plated second pole tip layer are partially consumed. During millingof the first pole piece layer to form the notches, the top and first andsecond side walls of the second pole tip layer are still furtherpartially consumed. During both milling times, milled material isredeposited on the side walls of the second pole tip. This is removed byangling the milling beam closer to a normal to the side walls. Thisprocess, referred to as clean-up, requires extra milling time. Becauseof the long processing time and large windage of the second pole tip itis difficult to keep the track width and the pole tip height withinacceptable limits. When the limits are exceeded, a wafer with literallythousands of magnetic head sites must be discarded. Further, increasingthe height of the plated second pole tip layer to account for windage,increases the aforementioned aspect ratios, making it difficult toconstruct a well-defined second pole tip with a submicron track width.Track widths 1 μm or less are desirable to increase tracks per inch(TPI) written on the disk.

Accordingly, there is a strong felt need to reduce the processing timerequired for notching, without sacrificing narrow track widths andquality of the write head.

SUMMARY OF THE INVENTION

We have discovered that a single-sided, notched write head writes narrowerase band servo tracks equally well as a double-notched write headsince the servo pattern is written with only one side of the write head.This produces a superior servo pattern compared to the conventionalmerge write head. For data performance, this implies that the singlesided notch head is not as good as the merged head for mitigating sideinterference, but is better than the dual-sided notched write head. Thesingle-sided notched write head will write a narrow erase band on thenotched side and a wide erase band on the side that is not notched. Inone embodiment, only one side of the first pole piece layer is notched,and in another embodiment, a first side of the first pole piece layer isnotched more than a second side thereof. In operation, the single-sided,notched write head is moved a distance less than the track width of thewrite head for each servo track written on the disk. For instance, ifthe write head is moved over one-half a track width for each servotrack, servo tracks can be written with a narrow erase band on each-sideof each servo track. Accordingly, the single-sided, notched write headcan write servo tracks equally well as a double-sided, notched writehead. Data tracks will be written with a narrow erase band on one sideand a wide erase band on the other side. This is a better configurationfor read head performance than one with a narrow erase band on bothsides of the data track. The wide erase band on one side of the datatrack allows greater flexibility in spacing the read head from adjacenttracks.

The construction of a single-sided, notched write head requires lesstime to construct than a double-sided, notched write head. We haveprovided several methods of construction. Generally, the windage of thesecond pole tip can be reduced by {square root over (2)}. In one method,the second pole tip is frame-plated on the gap layer, and photoresist isemployed for protecting a side of the first pole piece layer that is notto be notched. Milling is then employed for notching only one side ofthe first pole piece layer. With this arrangement, there is lessredeposition since material on only one side is milled. Accordingly, themilling time necessary for clean-up is shortened. Further, the workpiececan be oscillated back and forth 180° so that the notch site isliterally constantly milled, without being shadowed during 180° of therotation. The processing time is significantly reduced, reducing thewindage of the second pole tip. As stated hereinabove, less windagekeeps the desired track width and pole tip height within acceptablelimits. The method promotes constructing second pole tips with a trackwidth of 1 μm or less. Another method employs a notching layer on top ofthe first pole piece layer. The notching layer is slightly wider thanthe target track width, on the side to be notched, and has a widelateral expanse, on the side that is not to be notched. On the side tobe notched, a small corner of the notching layer is exposed beyond thesecond pole tip. Upon rotating the workpiece, the small corner isquickly milled away while the large expanse of the notching layer on theother side of the second pole tip is only slightly notched. Thisproduces an embodiment of the invention where one side of the first polepiece layer is notched significantly more than the other side.

An object of the present invention is to provide a single-sided, notchedwrite head that has the same servo writing capability as adouble-notched write head, but improved data writing capability.

Another object is to provide a method of making a notched write headthat requires less processing time than a double-notched write head forthe purpose of constructing a second pole tip with a track width of 1 μmor less.

A further object is to provide a notched write head that has abetter-defined, and narrower, second pole tip than a double-notchedwrite head.

Yet another object is to provide a method of notching a first pole piecewith more control of the target height and target track width of thesecond pole tip.

Still another object is to provide a method of notching a first polepiece of a write head with less consumption of a second pole tip, andwith less redeposited material to clean up after the notching.

Still a further object is to provide a method wherein single-sidednotching of a write head can be performed.

Still another object is to provide a single-sided, notched write headthat writes narrow erase band servo tracks equally as well as adouble-notched write head, writes data tracks better than adouble-notched write head, and requires less time to produce than adouble-notched write head.

Other objects and attendant advantages of the invention will beappreciated upon reading the following description taken together withthe drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a planar view of an exemplary magnetic disk drive;

FIG. 2 is an end view of a slider with a magnetic head of the disk driveas seen in plane II—II;

FIG. 3 is an elevation view of the magnetic disk drive wherein multipledisks and magnetic heads are employed;

FIG. 4 is an isometric illustration of an exemplary suspension systemfor supporting the slider and magnetic head;

FIG. 5 is a partial elevation view of the slider and magnetic head asseen in plane V—V of FIG. 2;

FIG. 6 is a view taken along plane VI—VI of FIG. 5 with all materialabove the second pole piece removed;

FIG. 7 is a partial ABS view of the'slider taken along plane VII—VII ofFIG. 5 to show the read and write elements of the magnetic head;

FIG. 8 is an ABS view of a prior art double-notched write head;

FIG. 9 is an ABS view of the present single notched write head;

FIG. 10 is an ABS view of another embodiment of the single notched writehead with a partial notch on an opposite side;

FIG. 11 is a schematic illustration of a servo pattern written by thesingle notched write head;

FIG. 12 is an ABS view of an initial step in the making of the prior artnotched write head;

FIG. 13 is an ABS view of the prior art double-notched write head aftermaking it with the prior art method;

FIG. 14 is an ABS view of a first step in the making of the singlenotched write head;

FIG. 15 is a view taken along plane XV—XV of FIG. 14;

FIG. 16 is a plan view taken along plane XVI—XVI of FIG. 14;

FIG. 17 is an ABS view showing the removal of a P1 seed layer;

FIG. 18 is an ABS view of the present method showing deposition of a gaplayer;

FIG. 19 is an ABS view of the present method showing frame plating thesecond pole tip;

FIG. 20 is an ABS view of the present method showing removal of secondpole piece material in the field;

FIG. 21 is an ABS view of the present method showing ion milling to forma single-sided notch with a partial notch on the other side;

FIG. 22 is similar to FIG. 21 except the first pole piece layer has beenslightly notched;

FIG. 23 is an ABS view of an overcoat layer on the embodiment of theinvention shown in FIG. 21;

FIG. 24 is an ABS view of an initial step of another embodiment of thepresent invention showing plating the second pole tip;

FIG. 25 is a plan view of FIG. 24 after forming a photoresist layer onthe workpiece with an opening exposing a work site;

FIG. 26 is a view taken along plane XXVI—XXVI of FIG. 25;

FIG. 27 is similar to FIG. 26 except ion milling is being employed forforming a single-sided notch of the present invention;

FIG. 28 is an ABS view of the completed magnetic head after forming theovercoat layer thereon;

FIG. 29 is a plan view of a further embodiment of the present inventionshowing a photoresist mask with an opening exposing a work site;

FIG. 30 is an ABS view of a plane taken along plane XXX—XXX of FIG. 29;

FIG. 31 is similar to FIG. 30 except ion milling has been employed tonotch the first pole piece;

FIG. 32 is an ABS view of the completed head with an overcoat layer;

FIG. 33 is an ABS planar view of still another method of the invention;

FIG. 34 is an ABS view taken along plane XXXIV—XXXIV of FIG. 33; and

FIG. 35 is an ABS view of the completed head with an overcoat layer.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, wherein like reference numerals designatelike or similar parts throughout the several views, there is illustratedin FIGS. 1-3 a magnetic disk drive 30. The drive 30 includes a spindle32 that supports and rotates a magnetic disk 34. The spindle 32 isrotated by a motor 36 that, in turn, is controlled by a motor controller38. A horizontal combined magnetic head 40 for reading and recording ismounted on a slider 42. The slider 42 is supported by a suspension 44and actuator arm 46. A plurality of disks, sliders and suspensions maybe employed in a large capacity direct access storage device (DASD), asshown in FIG. 3. The suspension 44 and actuator arm 46 position theslider 42 to locate the magnetic head 40 in a transducing relationshipwith a surface of the magnetic disk 34. When the disk 34 is rotated bythe motor 36, the slider is supported on a thin (typically, 0.05 μm)cushion of air (air bearing) between the disk and an air bearing surface(ABS) 48.

The magnetic head 40 may be employed for writing information to multiplecircular tracks on the surface of the disk 34, as well as for readinginformation therefrom. Processing circuitry 50 exchanges signalsrepresenting such information with the head 40, provides motor drivesignals, and also provides control signals for moving the slider 42 tovarious tracks. In FIGS. 1 and 4 the slider 42 is shown mounted to ahead gimbal assembly (HGA) 52 that is mounted to the suspension 44. Allof the above components are supported on a base 53.

FIG. 5 is a side cross-sectional elevation view of a mergedmagnetoresistive (MR) head 40, with a write head portion 54 and a readhead portion 56. The read head portion includes an MR sensor 58. The MRsensor 58 is sandwiched between first and second gap layers 60 and 62that are, in turn, sandwiched between first and second shield layers(S1) 64 and 66. In response to external magnetic fields, the resistanceof the MR sensor 58 changes. A sense current conducted through thesensor causes these resistance changes to be manifested as potentialchanges, which are processed by the processing circuitry 50 shown inFIG. 3.

The write head portion 54 of the head includes a coil layer 68sandwiched between first and second insulation layers (I1 and I2) 70 and72. A third insulation layer (I3) 74 may be employed for planarizing thehead to eliminate ripples in the second insulation layer caused by thecoil layer 68. The first, second and third insulation layers arereferred to as an “insulation stack”. The coil layer 68, and the first,second and third insulation layers 70, 72 and 74, are sandwiched betweenfirst and second pole piece layers (S2/P1) 76 and (P2) 78. The first andsecond pole piece layers 76 and 78 are magnetically coupled at a backgap 80, and have first and second pole tips 82 and 84 that are separatedby a non-magnetic gap layer (G3) 86 at the ABS. As shown in FIGS. 2 and4, first and second solder connections 88 and 90 connect leads (notshown) from the MR sensor 58 to leads 96 and 98 on the suspension 44;third and fourth solder connections 100 and 102 connect leads 104 and106 from the coil 68 (see FIG. 6) to leads 108 and 110 on thesuspension.

One or more sectors of the magnetic disk are dedicated for servoing. Thewrite head writes servo tracks in these sectors, which are read by theread head to position the magnetic head on the disk. It is desirablethat the servo tracks be separated by narrow erase bands in order toobtain greater precision in servoing. An erase band defines a crosstrack distance between magnetic servo signals.

Narrow erase bands are desirable in servo tracks. Wide erase bandssacrifice servo signal amplitude, and also contribute to position errorsignal (PES) non-linearity. A write head with no notching produces servotracks with large erase bands. In some disk files, wide erase bandsreduce the servo signal by as much as 40% of the full track amplitude.This may exceed a limit of acceptability and result in a significantmanufacturing yield loss.

FIG. 8 shows a prior art magnetic head 120 with a double-notchedstructure that produces narrow erase bands. The first pole piece layer66/76 has been notched on both sides of a second pole tip 122 to form apedestal 124 with first and second sides 126 and 128. On the pedestal124 is a gap layer 130 that has first and second sides 132 and 134. Onthe gap layer 130 is the second pole tip with first and second sides 136and 138. The first side walls 136. 132 and 126 of the layers arecontiguous and the second side walls 138, 134 and 128 of the layers arecontiguous. With this arrangement, there is very little side writingbecause the flux from the second pole tip 122 is transferred to thepedestal 124, rather than to large lateral expanses 142 and 144 of thefirst pole piece layer. This enables the notched write head to writeservo tracks with narrow erase bands. The disadvantage with thedouble-notched write head 120 is that data tracks written by the headalso have narrow erase bands, leaving little room for error inpositioning the read head over a written track, and increasing thelikelihood that the read head will pick up data information fromadjacent tracks.

In FIG. 9, there is shown the present single notched write head 150. Thefirst pole piece layer 66/76 has a raised portion 152 that has a firstside wall 154. On the raised portion 152 is a gap layer 156 that has afirst side 158. On the gap layer 156 is a second pole tip 162 that hasfirst and second sides 164 and 166. In the single notched write head,the first sides 164, 158 and 154 of the layers are contiguous, while theraised portion 152 on the other side of the second pole tip 162 has alarge lateral expanse 168. With the present magnetic head, the eraseband on the left side of the second pole tip 162 will be narrow, whilethe erase band on the right side thereof will be wide. It should benoted, however, that the single-notched write head 150 can write a servopattern of the same quality as the double-notched write head 120 in FIG.8, as explained in the next paragraph.

FIG. 11 shows a servo pattern that can be written by the single-sided,notched write head 150, with narrow erase bands shown at 170. The servopattern may be formed by writing exemplary all ones transitions in thefirst path, for example. The head is then moved in the cross-trackdirection, by a small amount, which is less than the track width. Thesame pattern is written in phase with the previously-written adjacenttrack. This process is repeated from the ID to the OD of the disk. Thereduction in the side writing field substantially eliminates the erasebands in the phase aligned patterns. Such patterns significantlyincrease the magnitude of the servo signal, and improve position errorsignal (PES) linearity, which ultimately increases file yield. Sinceservo patterns can be formed by overwriting previously written trackswith one edge of the pole tip, a single-sided, notched write head canwrite servo patterns with the same high quality as the double-notchedwrite head 120 in FIG. 8.

Another embodiment 172 of the present invention, shown in FIG. 10, isnotched in the same manner on the left side of the pole tip 154, withfirst side walls 164, 158 and 154 of the layers contiguous. Theembodiment 172 differs from the embodiment 150 in that the first polepiece layer 66/76 has a partial notch 174 on the opposite side of thesecond pole tip 162. The embodiment 172 is a result of one of thepresent methods of making the single notched write head which isdescribed hereinafter. Accordingly, the embodiment in 172 is considereda single notched write head from the standpoint that the notching depthat 154 is significantly greater than the notching depth at 174. In anyevent, the broad concept of the single-sided notched write head includesdouble-notching where one notch is a greater depth than the other notch,as shown in FIG. 10, as well as no notching on one side, as shown inFIG. 9. The embodiment 172 has essentially the same advantage in writinga narrow-erase banded servo pattern as the embodiment 150.

One advantage of the embodiments shown in FIGS. 9 and 10 is that theycan write better data tracks than the prior art double-notched writehead 120 in FIG. 8. A data track written by either of the embodiments inFIGS. 9 and 10 will have a narrow erase band on one side, and a wideerase band, on an opposite side, of the second pole tip. This is incontrast to a data track written by the prior art magnetic head 120which writes the data track with a narrow erase band on each side of thetrack. A data track written by the prior art magnetic head 120 is closerto adjacent tracks, which can lead to a read head picking up datasignals from adjacent tracks, thereby resulting in poor dataperformance. There is a wider band between adjacent data tracks writtenby the present embodiments 150 and 172, thereby minimizing pick up bythe read head from adjacent tracks. Other advantages of the presentembodiments 148 and 158 lie in the methods of making, describedhereinafter.

FIGS. 12 and 13 show a prior art method of making a prior art mergedmagnetic head, wherein the second shield of the read head and the firstpole piece of the write head are a common layer 66/76. The gap layer 180has been formed on the first pole piece layer 66/76, followed by frameplating a second pole tip 182 on the gap layer 180. The second pole tip182 is a front portion of the second pole piece, exposed at the ABS, asseen in FIG. 12. The second pole tip is bounded by a top 184, first andsecond side walls 186 and 188, and a base 190. The target track width(TW) is shown in FIG. 12. Since the first pole piece 66/76 will benotched by ion milling, the second pole tip 182 is wider than a targetsize track width (TW), and higher than a target height of the finalsecond pole tip, so as to allow for consumption of the second pole tipduring a subsequent milling cycle. Accordingly, before milling, thefirst and second side walls 186 and 188 extend beyond the target trackwidth (TW), and the top 184 is higher than the target height. Thedimensions of these sacrificial portions is referred to in the art aswindage.

In FIG. 13 ion milling is employed to mill through the gap layer to forma write gap 191 with first and second side walls 192 and 194 and to millnotches into the first pole piece 66/76 with first and second side walls196 and 198. After milling, the first side walls 186, 192, and 196 arecontiguous, and the second side walls 188, 184 and 198 are contiguous.This notching improves the transfer of flux between the second pole tip122 and the first pole piece 66/76, since the flux will go to thepedestal portion of the first pole piece, instead of to the largerexpanse thereof. This improves side writing. The milling beam is angledwith respect to a normal to the layers 66/76 and 64, in order tominimize redeposition of the milled material. The angle of the beam istypically 20°-35°. It should be understood that the partially completedmagnetic head in FIG. 12 rests upon a substrate (not shown), which isrotated during the milling cycle. The second pole tip 182 is employed asa mask for forming the write gap 190 and notching the first pole pieceat 196 and 198. Because of the angled milling, the second pole causesshadowing at the notching sites 136 and 138 during approximately 180° ofthe rotation. This shadowing increases the processing time required toform the notches 196 and 198 in the first pole piece 66/76. The downwardsloping portions of the first pole piece layer 66/76 in FIG. 13 are dueto the shadowing by the second pole tip 122.

After milling, the second pole tip 182 has been reduced to the sizeshown in FIG. 13. With the prior art method it is difficult to reducethe second pole tip 182 to the target track width and the target heightbecause of the significant time required for milling the large lateralexpanse of the first pole tip 66/76. Milling of flat surfaces is verytime-consuming as compared to milling side walls. Further, the extraheight of the top 184 of the second pole tip in FIG. 12 increases theaspect ratio (ratio between height of resist employed to frame plate thesecond pole tip 182 and the target track width), which reduces the linewidth of the second pole tip. Prior art methods of notching the firstpole piece are discussed in commonly assigned U.S. Pat. Nos. 5,438,747and 5,452,164. A strong-felt need is manifested in these references toreduce the time required to notch the first pole piece of a write head.

FIGS. 14-23 illustrate a first method of the invention, which implementssingle-sided notching of the first pole piece 66/76. In FIG. 14, anotching layer 250 (PIN) is frame plated on the first pole piece layer200. The first pole piece includes the first pole piece layer 200 andthe notching layer 250. The notching layer 250 has a top 252 and a firstside wall 254. The notching layer 250 has a large expanse, which maycoincide with the lateral expanse of the first pole piece layer 200 asit extends away from the first side wall 254. Accordingly, the notchinglayer 250 has only one corner formed by the side wall 254 which ismilled in a subsequent step for notching purposes.

Two embodiments of a planar shape of the notching layer 250 are shown inFIGS. 15 and 16. In FIG. 15, the second pole piece is shown in phantomat 260, with a pole tip region 262, a flare region 264 and a yoke region266, the commencement of the flare region 264 being shown at flarepoints 268 and 270. In this embodiment the flare point 268, which is onthe side where the notching layer 250 is to be notched, is recessedfarther into the head than the flare point 270. Accordingly, the notchedlayer 250 is provided with an inside corner 272 which is adjacent to theflare point 268 and matches the flare 264 back to the yoke region 266.On the other side of the pole tip region 262, where the flare point 270is located notching will not be implemented, and the notching layer 250provides a wide lateral expanse extending from the pole tip region 262.In this embodiment, the notching layer 250 is frame plated with a planarshape, as shown in FIG. 15.

Another embodiment of the notching layer 250 is shown in FIG. 16. Inthis embodiment the second pole piece 274 has a pole tip region 276, aflare region 278 and a yoke region 280. The flare region 278 commencesat flare points 282 and 284. In this embodiment, the notching layer 250has an inside corner 286 which is adjacent the flare point 282 andextends along just the outside of the flare region 278 and the yokeregion 280. The notching layer 250 on the opposite side of the pole tipregion 276 has a large lateral expanse, the same as the notching layerin FIG. 15.

The difference between FIGS. 15 and 16 is that the flare region in FIG.15 is asymmetrical and the flare region in FIG. 16 is symmetrical. Theembodiment shown in FIG. 15 has an advantage from a processingstandpoint in that the second pole piece 260 on the side of the notchedlayer to be notched is recessed further into the head so as to minimizeshadowing by the second pole piece when the notched layer is milled,which will be described in more detail hereinafter. This advantage hasto be balanced with the magnetics of the head as compared to the typicalsymmetrical flare region 286 shown in FIG. 16. At this point in theprocess, the second pole piece 266 in FIG. 15 and the second pole pieceat 280 in FIG. 16 have not been formed.

In FIG. 17, the first pole piece seed layer is removed which causes aslight rounding of the upper corner of the notched layer 250. Next, agap layer 290 is deposited along with a first insulation layer (notshown), a coil layer (not shown), a second insulation layer (not shown)and a third insulation layer (not shown). The first insulation layer,the coil layer, the second insulation layer and the third insulationlayer can be seen in FIG. 5 at 70, 68, 72 and 74 respectively. The gaplayer 290 is a full film layer which covers the entire top 252 of thenotching layer, the side 254 of the notching layer and the remaininglateral expanse of the first pole piece layer.

The next step is to frame plate the second pole piece along with asecond pole tip 292, as shown in FIG. 19. The second pole tip 292 isbounded by a top 294, first and second side walls 296 and 298 and a base300. As stated hereinabove, the thickness and width of the second poletip 292 are enlarged to account for erosion by processing steps,including the subsequent milling step for notching the notching layer250. In FIG. 20 a resist layer 302 is formed on top of the second poletip, and second pole piece material located in the field is removed bychemical etching. In FIG. 21 ion milling is implemented at an angle to anormal to the planes of the layers 64 and 200, this angle beingpreferably 20° to 35°, as discussed hereinabove. This milling reducesthe gap layer 290 in FIG. 20 to form a write gap layer 304 with firstand second side walls 306 and 308. The milling continues until the firstside walls 296, 306 and 254 are contiguous. This milling causes a veryslight notching in the large lateral expanse of the notching layer 250,forming a very small side wall 310. For all practical purposes, thefirst pole piece has been provided with a single notch at 254. In FIG.22 a longer milling cycle is employed to notch into the first pole piecelayer 200 to form a first side wall 314. In this embodiment, the millingcycle is employed until the first side walls 296, 306, 254 and 314 arecontiguous. The notching layer on the other side of the pole tip wouldbe slightly notched, as shown at 316. The preferred embodiment is shownin FIG. 21, since less milling time is required, which embodiment isshown formed with an overcoat in FIG. 23. The method shown in FIGS.14-23 permits the first pole piece to be constructed of materials withdifferent magnetic moments. For instance, the first piece layer 200 canbe Ni₈₀Fe₂₀ and the notching layer can be Ni₄₅Fe₅₅ or the first polelayer 200 can be Ni₄₅Fe₅₅ and the notching layer can be Ni₈₀Fe₂₀.

Another embodiment of making the single-sided, notched write head isshown in FIGS. 24-28. After forming a gap layer 400 on the first polepiece layer 66/76, a second pole piece including a second pole tip 402is formed on the gap layer. The second pole tip 402 has first and secondside walls 404 and 406 and a top 408. The second side wall 406 isaligned with the right side of the track width, and the first side wall406 is extended beyond the left side of the track width, since it is theside that will be partially consumed by milling. A photoresist mask 410is then formed on the workpiece covering all of the second pole piece aswell as the second pole tip 402 with an opening 412. As can be seen fromFIG. 25, the opening extends along one side of the second pole tip 402from a flare point 414 to a location beyond the ABS 416. The opening 412extends laterally a sufficient distance so that angled milling will beable to notch the first pole piece layer 66/76. FIG. 26 shows the resistmask 410 protecting a right lateral expanse of the gap layer 400, thesecond side wall 406 and the top 408 of the second pole tip 402. Asshown in FIG. 25, the workpiece may be rotated 360°, as shown at 418, oroscillated back and forth approximately 180°, as shown at 420. Duringfull rotation or oscillation, ion milling is employed to mill throughthe gap layer 400 to form the gap layer with a first side wall 422 andnotch the first pole piece layer 66/76 with a first side wall 424. Thefirst side wall 404 of the second pole tip is milled until it is alignedat its base with the left side of the track width (TW), and until it iscontiguous with the first side wall 422 of the gap layer and the firstside wall 424 of the first pole piece layer. The right side wall 406 ofthe second pole tip, the top 408 and the gap layer 400 extending fromthe side wall 406 remain untouched by the milling. Even with fullrotation 418, shown in FIG. 25, ion milling in the present inventionproduces less redeposition and therefore requires less milling time toclean up redeposited material after the notches have been formed, ascompared to the prior art method. The milling time is still furtherdecreased when the workpiece is oscillated, as shown at 420 in FIG. 25.When the workpiece is oscillated the notch site is subjected to ionmilling substantially 100% of the time. It should be noted, with bothrotations, that the top 408 has not been milled, which decreases theheight of the second pole tip 402 plated in FIG. 24. Reduction of theheight of the pole tip reduces the aspect ratio and promotesconstruction of a more well-defined, narrow track width second pole tip.Track widths 1 μm or less can be achieved. The next step is to removethe resist mask 410 and form an overcoat layer 426 on the workpiece, asshown in FIG. 28.

Another method of making the notched write head is shown in FIGS. 29-32,which is a modification of the method shown in FIGS. 24-28. The firststep of this method is the same step as shown in FIG. 24 for theprevious method. This method differs from the previous method in that aresist mask 450 is provided with a larger opening 452 exposing thesecond pole tip 402, as well as a portion of the gap layer 400. Thismethod is shown to illustrate that the opening 452 does not have to belocated adjacent the first side wall 404 of the second pole tip, asshown in FIG. 25, in order to achieve satisfactory notching of the firstpole piece 66/76. FIG. 30 shows an ABS view of the workpiece prior toion milling. In this method it is preferable to oscillate the workpiecesubstantially 180° as shown at 454 in FIG. 29. While oscillating theworkpiece, ion milling is implemented, as shown in FIG. 31. In thisembodiment the gap layer 400 will be milled to form the gap layer with afirst side wall 422, and the first pole piece layer 66/76 will benotched to form it with a first side 424. The first side wall 404 of thesecond pole tip is milled in slightly. The milling is continued untilthe first side wall 404, the first side wall 422 of the gap layer andthe first side wall 424 of the first pole piece layer are contiguous,and until the first side 404 of the second pole tip aligns with the leftside of the track width. In this embodiment the top 408 is milled downslightly, which requires the second tip 402 to be plated with an extrathickness in the plating step shown in FIG. 24. The next step is toremove the resist mask 450 and form an overcoat layer 456 on theworkpiece, as shown in FIG. 32.

Another method of constructing the single-sided, notched write head isshown in FIGS. 33-35. This method differs from the previous methods inthat a resist mask is not employed. The first step is to plate thesecond pole piece and second pole tip 402, as shown in FIG. 24. In thismethod the workpiece is oscillated back and forth substantially 180°, asshown at 500 in FIG. 33. While oscillating the workpiece, ion milling isimplemented. As with the previous method, this method mills through thegap layer to form the gap layer 400 with a first side wall 492, andnotches the first pole piece layer to form a first side wall 424. Thefirst side wall 424 of the second pole tip is milled in slightly untilit is aligned with the left side of the track width (TW) and until thefirst side wall 404 of the second pole tip, the first side wall 422 ofthe gap layer and the first side wall 424 of the first pole piece layerare contiguous, as shown in FIG. 34. In this embodiment, the top 408 ofthe second pole tip will be milled down slightly, requiring the secondpole tip 402 to be plated with an extra thickness in the plating stepshown in FIG. 24. Further, in this embodiment there will be moreredeposited material on the second side 406 of the second pole tip,requiring an ion milling step to perform clean-up. To implementclean-up, the ion milling angle is increased to about 65° from a normalto the planes of the layers. The next step is to form an overcoat layer506 on the workpiece, as shown in FIG. 35.

Clearly, other embodiments and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. Therefore, this invention is to be limited only by thefollowing claims, which include all such embodiments and modificationswhen viewed in conjunction with the above specification and accompanyingdrawings.

We claim:
 1. A magnetic head assembly having an air bearing surface(ABS), comprising: a write head, including: a first pole tip layer and anotching, layer, which are separate layers, the notching layer being onthe first pole tip layer and having a width at the ABS that is smallerthan a width of the first pole tip layer at the ABS; a second pole tiplayer; a gap layer sandwiched between the notching layer and the secondpole tip layer; each of the second pole tip layer and the gap layerhaving first and second side walls that terminate at the ABS; thenotching layer having a first side wall that has a height, and no secondside wall, or a second side wall that has a height less than said heightof the first side wall; and the first side walls being contiguous andthe second side walls being contiguous.
 2. A magnetic head assembly asclaimed in claim 1, wherein the notching layer has a second side wall.3. A magnetic head assembly as claimed in claim 1, wherein the magnetichead assembly further includes; a first pole piece layer; a firstinsulation layer on the first pole piece layer; a coil layer on thefirst insulation layer; at least a second insulation layer on the coillayer; and a second pole piece layer on the second insulation layer. 4.A magnetic head assembly as claimed in claim 3, further comprising: aread head including: a magnetoresistive (MR) sensor, first and secondleads connected to the MR sensor and first and second gap layers; the MRsensor and the first and second leads being sandwiched between the firstand second gap layers; first shield layer; and the first and second gaplayers being sandwiched between the first shield layer and the firstpole tip layer.
 5. A magnetic head assembly as claimed in claim 4,wherein the notching layer has a thickness between 0.2 μm to 1.0 μm. 6.A magnetic head assembly as claimed in claim 5, wherein the notchinglayer has a second side wall.
 7. A magnetic disk drive, comprising: amagnetic head assembly with an air bearing surface (ABS); a write headin the magnetic head assembly, the write head including: a first poletip layer and a notching layer, which are separate layers, the notchinglayer being on the first pole tip layer and having a width at the ABSthat is smaller than a width of the first pole tip layer at the ABS; afirst insulation layer on the first pole tip layer; a coil layer on thefirst insulation layer; at least a second insulation layer on the coillayer; a second pole tip layer on the second insulation layer; a gaplayer sandwiched between the notching layer and the second pole liplayer, each of the second pole tip layer and the gap layer having firstand second side walls that terminate at the ABS; the notching layerhaving a first side wall that has a height, and no second side wall, ora second side wall that has a height less than said height of the firstside wall; and the first side walls being contiguous and the second sidewalls being contiguous, a read head in the magnetic head assembly, theread head including: a magnetoresistive (MR) sensor, first and secondleads connected to the MR sensor and first and second gap layers; the MRsensor and the first and second leads being sandwiched between the firstand second gap layers; a first shield layer; and the first and secondgap layers being sandwiched between the first shield layer and the firstpole tip layer; a frame; a magnetic disk rotatably supported on theframe; a support mounted on the frame for supporting the magnetic headassembly in a transducing relationship with the magnetic disk; means forrotating the magnetic disk; positioning means connected to the supportfor moving the magnetic head assembly to multiple positions with respectto said magnetic disk; and means connected to the magnetic headassembly, to the means for rotating the magnetic disk and to thepositioning means for exchanging signals with the magnetic headassembly, for controlling movement of the magnetic disk and forcontrolling the position of the magnetic head assembly.
 8. A magneticdisk drive as claimed in claim 7, wherein the notching layer has asecond side wall.
 9. A magnetic disk drive as claimed in claim 7,wherein the notching layer has a thickness between 0.2 μm to 1.0 μm. 10.A magnetic head assembly that has an air bearing surface (ABS),comprising: a write head in the magnetic head assembly, the write headincluding: a first pole tip layer and a notching layer, which areseparate layers, the notching layer being on the first pole tip layerand having a width at the ABS that is smaller than a width of the firstpole tip layer at the ABS; a first insulation layer on the first poletip layer; a coil layer on the first insulation layer; at least a secondinsulation layer on the coil layer; a second pole tip layer on thesecond insulation layer; a gap layer sandwiched between the notchinglayer and the second pole tip layer; each of the second pole tip layerand the gap layer having first and second side walls that terminate atthe ABS; the notching layer having a first side wall that has a height,and no second side wall, or a second side wall that has a height lessthan said height of the first side wall; and the first side walls beingcontiguous and the second side walls being contiguous; a read head inthe magnetic head assembly, the read head including: a magnetoresistive(MR) sensor, first and second leads connected to the MR sensor and firstand second gap layers; the MR sensor and the first and second leadsbeing sandwiched between the first and second gap layers; a first shieldlayer; and the first and second gap layers being sandwiched between thefirst shield layer and the first pole tip layer.
 11. A magnetic headassembly as claimed in claim 10, wherein the notching layer has a secondside wall.
 12. A magnetic head assembly as claimed in claim 10, whereinthe notching layer has a thickness between 0.2 μm to 1.0 μm.
 13. Amagnetic head assembly having an air bearing surface (ABS), comprising:a write head, including: a first pole tip layer and a notching layer,which are separate layers, the notching layer being on the first poletip layer and having it width at the ABS that is smaller than a width ofthe first pole tip layer at the ABS; a second pole tip layer; a gaplayer sandwiched between the notching layer and the second pole tiplayer; each of the second pole tip layer and the gap layer having firstand second side walls that terminate at the ABS; the notching layerhaving a first side wall that has a height, and no second side wall, ora second side wall that has a height less than said height of the firstside wall; and the first side walls being contiguous with uninterruptedcontinuity and the second side walls being contiguous with uninterruptedcontinuity.
 14. A magnetic disk drive, comprising: a magnetic headassembly with an air bearing surface (ABS); a write head in the magnetichead assembly, the write head including: a first pole tip layer and anotching layer, which are separate layers, the notching layer being onthe first pole tip layer and having a width at the ABS that is smallerthan a width of the first pole tip layer at the ABS; a first insulationlayer on the first pole tip layer; a coil layer on the first insulationlayer; at least a second insulation layer on the coil layer; a secondpole tip layer on the second insulation layer; a gap layer sandwichedbetween the notching layer and the second pole tip layer; each of thesecond pole tip layer and the gap layer having first and second sidewalls that terminate at the ABS; the notching layer having a first sidewall that has a height, and no second side wall, or a second side wallthat has a height less than said height of the first side wall; and thefirst side walls being contiguous with uninterrupted continuity and thesecond side walls being contiguous with uninterrupted continuity; a readhead in the magnetic head assembly, the read head including: amagnetoresistive (MR) sensor, first and second leads connected to the MRsensor and first and second gap layers; the MR sensor and the first andsecond leads being sandwiched between the first and second gap layers; afirst shield layer; the first and second gap layers being sandwichedbetween the first shield layer and the first pole tip layer; a frame; amagnetic disk rotatably supported on the frame; a support mounted on theframe for supporting the magnetic head assembly in a transducingrelationship with the magnetic disk; means for rotating the magneticdisk; positioning means connected to the support for moving the magnetichead assembly to multiple positions with respect to said magnetic disk;and means connected to the magnetic head assembly, to the means forrotating the magnetic disk and to the positioning means for exchangingsignals with the magnetic head assembly, for controlling movement of themagnetic disk and for controlling the position of the magnetic headassembly.
 15. A magnetic head assembly that has an air bearing surface(ABS), comprising: a write head in the magnetic head assembly, the writehead including: a first pole tip layer and a notching layer, which areseparate layers, the notching layer being on the first pole tip layerand having a width at the ABS that is smaller than a width of the firstpole tip layer at the ABS; a first insulation layer on the first poletip layer; a coil layer on the first insulation layer; at least a secondinsulation layer on the coil layer; a second pole tip layer on thesecond insulation layer; a gap layer sandwiched between the notchinglayer and the second pole tip layer; each of the second pole tip layerand the gap layer having first and second side walls that terminate atthe ABS; the notching layer having a first side wall that has a height,and no second side wall, or a second side wall that has a height lessthan said height of the first side wall; and the first side walls beingcontiguous with uninterrupted continuity and the second side walls beingcontiguous with uninterrupted continuity; a read head in the magnetichead assembly, the read head including: a magnetoresistive (MR) sensor,first and second leads connected to the MR sensor and first and secondgap layers; the MR sensor and the first and second leads beingsandwiched between the first and second gap layers; a first shieldlayer; and the first and second gap layers being sandwiched between thefirst shield layer and the first pole tip layer.